Lunar missions over the last decade have revealed the complexity of the lunar crust and the near surface environment of the Moon. Space based remote sensing measurements provide vital clues to understand the global evolution of the Moon by mapping the distribution of elements and minerals on the lunar surface in
multi-wavelengths. The surface chemistry of the Moon can be well explored in
X-rays using the X-ray Fluorescence (XRF) technique. Observational evidences help to test models of lunar evolution from the formation to the chemical
diversity of the Moon. Indian lunar space missions (Chandrayaan-1, 2) have
their modest contributions to th is field and ambitious plans for the future. The X-ray spectrometer (C1XS) on-board Chandrayaan-1 was designed to map the
global abundances of rock-forming elements (Mg, Al, Si, Ca, Ti and Fe) over
the lunar surface. C1XS observations revealed the evidence of enhanced Na abundances for the first time, from differentparts of the Moon. In this talk I
will present an overview of C1XS instrument, its observations and highlight the
results. Further, I will also show how the lessons learned from C1XS are transformed into the design and development of the upcoming X-ray instrument: CLASS for the second Indian Moon mission Chandrayaan-2.